Optical defect amplification for improved sensitivity on patterned layers

ABSTRACT

A method for wafer defect inspection may include, but is not limited to: providing an inspection target; applying at least one defect inspection enhancement to the inspection target; illuminating the inspection target including the at least one inspection enhancement to generate one or more inspection signals associated with one or more features of the inspection target; detecting the inspection signals; and generating one or more inspection parameters from the inspection signals. An inspection target may include, but is not limited to: at least one inspection layer; and at least one inspection enhancement layer.

RELATED APPLICATIONS

This application claims priority to Patent Cooperation TreatyApplication No. PCT/US10/42148 filed on Jul. 15, 2010 which claimspriority to U.S. Provisional Application Ser. No. 61/226,260 filed onJul. 16, 2009, all of which are hereby incorporated by reference intheir entirety.

BACKGROUND

This invention deals with improving the sensitivity of defect inspectionon patterned surfaces where the patterned structures are not fabricatedas intended. The inspection of these surfaces may involve directinglight onto such surfaces, collecting light from the surface andprocessing the collected light to determine whether defects are present.An example of this can be in semiconductor wafer manufacturing wherethin-film layers are processed with lithography creating patterns in thesurface that are subsequently etched and processed to createsemiconductor devices. In the lithography process, a layer ofphotoresist is deposited on the surface and the photoresist isilluminated with a pattern that is developed and processed to establisha pattern that will be etched into the surface to create a layer for thesemiconductor device. Defects within photoresist layers are an exampleof low-signal producing defects where some amplification of detectionsignals may be required to adequately identify defects. This need may behigher when considering the extreme ultraviolet (EUV) lithographyrequirements for detecting printed defects from the mask. Prior methodsfor accounting for low level signals included optimization of theinspection parameters of light, spectral band, aperture mode and toolspeed/pixel to identify an optimal inspection recipe.

However, such optimizations may be insufficient for detecting signallevels on print-check wafers (sometimes called “flop-down wafers”)resulting from ever-smaller defects in future design rules (DR) (e.g. a15 nm DR having allowed excursions of 1/10 of the line width or 1.5 nm)established from EUV mask inspection requirements.

SUMMARY

A method for wafer defect inspection may include, but is not limited to:providing an inspection target; applying at least one defect inspectionenhancement to the inspection target; illuminating the inspection targetincluding the at least one inspection enhancement to generate one ormore inspection signals associated with one or more features of theinspection target; detecting the inspection signals; and generating oneor more inspection parameters from the inspection signals.

It is to be understood that both the foregoing general description andthe following detailed description may be exemplary and explanatory onlyand may be not necessarily restrictive of the invention as claimed. Theaccompanying drawings, which may be incorporated in and constitute apart of the specification, illustrate embodiments of the invention andtogether with the general description, serve to explain the principlesof the invention.

BRIEF DESCRIPTION OF THE DRAWINGS

The numerous advantages of the disclosure may be better understood bythose skilled in the art by reference to the accompanying figures inwhich Figure Number:

1 shows a cross-sectional profile of a wafer surface with a periodicstructure and a defect;

2A shows signal responses for an inspection system operating in abrightfield mode as a function of wavelength for various defectinspection enhancement layer materials;

2B shows signal responses for an inspection system operating in adarkfield mode as a function of wavelength for various inspectionenhancement layer materials;

3 shows signal values using the best inspection band/mode recipe forvarious inspection enhancement layers;

4A shows inspection permittivity as a function of inspection wavelength;

4B shows inspection permittivity as a function of inspection wavelength;

5 shows a cross-sectional profile of a wafer surface with a periodicstructure and a defect;

6 shows signal responses as a function of wavelength for variousinspection enhancement layer thicknesses;

7 signal response as a function of the depth of a SiN inspectionenhancement layers for 313 nm and 365 nm inspection wavelengths;

8 shows a process for pattern transfer of one inspection target layerinto another inspection target material;

9 shows a signal response as a function of patterned inspectionenhancement layer thickness for various patterned inspection enhancementlayer materials;

10 shows a signal response as a function of inspection wavelength forvarious inspection enhancement layer thicknesses; and

11 shows a signal response as a function of resist refractive index nand extinction index k for both reflective and absorptive underlayers.

DETAILED DESCRIPTION OF THE INVENTION

In the following detailed description of exemplary embodiments,reference is made to the accompanying drawings, which form a parthereof. In the several figures, like referenced numerals identify likeelements. The detailed description and the drawings illustrate exemplaryembodiments. Other embodiments may be utilized, and other changes may bemade, without departing from the spirit or scope of the subject matterpresented here. The following detailed description is therefore not tobe taken in a limiting sense, and the scope of the claimed subjectmatter is defined by the appended claims.

Brightfield microscopes (e.g. a 2830 Brightfield Patterned Wafer DefectInspection System produced by KLA-Tencor Corporation, Milpitas, Calif.)may be employed to image the wafer's surface. Such devices may operatein several modes including: (1) brightfield mode where the specularreflection from a surface of an inspection target and any propagatingdiffraction modes that returned to the microscope aperture may becaptured thereby measuring the loss via signal inspection that it is notreturned to the microscope; (2), unresolved dark-field (DF) mode wherethe wafer's surface is imaged and scattered light from the defect andscattered signals from random noise events are captured; and (3)resolved DF where an image of the wafer's surface may contain bothscattered light from the defect as well as diffracted orders from thestructure.

It may be the case that a number of layers may be difficult to inspectusing because the materials may produce small signals (e.g. lithographylayers where photoresist is a poor scatterer of light). Additionally,defects are getting smaller as lithography tools advance theircapabilities to allow smaller patterns to be created making inspectionof such layers even more challenging because smaller defects generallyproduce less signal than larger defects.

Recent improvements in EUV lithography indicate that it might be aviable option for future generations of lithography. Detection of phasedefects, caused by either bumps and/or holes in the substrate orparticles deposited during multilayer coatings needed to make thesubstrate reflecting at the EUV wavelength is important to thedevelopment of defect-free masks. Defect free masks are needed so thatmask defects do not propagate into the photoresist and resulting indefective semiconductor devices. However, masks and mask substrates forthe EUV process are opaque to UV and visible wavelengths. In such cases,actinic (EUV wavelength) inspection may be required to be sensitive tothese defects. However, if an exposed and developed photoresist wafercould be inspected with enough sensitivity to detect all the defectsresulting from the mask, it may serve satisfy the requirements forqualification and recertification of the EUV mask itself.

Another candidate for next generation lithography may be nano-imprintlithography (NIL) which uses a multiple-use template that may be pressedinto the photoresist establishing a pattern in photoresist. Again,having a wafer inspection tool with sufficient sensitivity to qualifythe NIL mask through inspection of a resulting printed wafer may be moreattractive than building a dedicated tool to inspect the parent andchild NIL molds.

The below described invention provides methods of enhancing resultantsignals produced from wafer layers of an inspection target (i.e.“inspection layers”) subject to optical defect inspection which have alow signal response (e.g. photoresist layers). For example, one or moreinspection enhancements may be applied to an inspection target toenhance the detectability of defects in various inspection layers ofthat inspection target. For example, as described below, an inspectionenhancement may include at least one of an application of an topicalinspection enhancement layer over an inspection layer, an application ofan inspection enhancement underlayer beneath an inspection layer,transfer of a patterned layer of the inspection target to an inspectionenhancement layer of a second inspection target and/or selection ofinspection layer materials exhibiting particular optical properties.

Following application of an inspection enhancement to an inspectiontarget, the inspection target may be subjected to inspection by aninspection tool. For example, an inspection tool (e.g. a 2830Brightfield Patterned Wafer Defect Inspection System produced byKLA-Tencor Corporation, Milpitas, Calif.) may be used to illuminate aninspection target which as been subjected to an inspection enhancementwith electromagnetic radiation across various spectral bands to generateone or more inspection signals (e.g. reflected signals, scatteredsignals, and the like) associated with one or more physical features ofthe inspection target. Those inspection signals may be detected by theinspection tool and analyzed to produce one or more inspectionparameters indicative of the physical features of the inspection target.

Reference will now be made in detail to the subject matter disclosed,which is illustrated in the accompanying drawings.

For example, FIG. 1 shows a cross-sectional view of an inspection target100 patterned to include a line-space array of parallel lines. Theinspection target 100 may include an inspection layer 101 (e.g. aphotoresist layer subject to inspection) including one or more defectstructures 102, to which a topical inspection enhancement layer 103A maybe applied. The topical inspection enhancement layer 103A may haveincreased inspection properties relative to the inspection layer 101(e.g. enhanced reflectivity, scattering, refractive index, etc.). Theapplication can be done with a deposition tool such as a chemical vapordeposition process. The increased scattering capabilities of the topicalinspection enhancement layer 103A may enhance the scattering signal dueto its material properties. For example, a metallic defect will scattermuch more light than a dielectric defect. Such a topical inspectionenhancement layer 103A may also serve to increase the volume of aparticular defect, thereby further increasing the scattering associatedwith that defect.

Various materials may be used to coat a wafer to provide a topicalinspection enhancement layer 103A. Referring to FIGS. 2A and 2B,representative scattering signals using various topical inspectionenhancement layer 103A materials are shown. For example, materialsincorporated into the topical inspection enhancement layer 103A mayinclude, but are not limited to titanium nitride, aluminum, silver,gold, tantalum nitride and/or chromium. It should be noted that sometopical inspection enhancement layer 103A materials may include thosethat are commonly used in wafer fabrication processes for other purposes(e.g. adhesion layers). FIGS. 2A and 2B show the respective signals(e.g. in gray levels (GL) out of a possible 255) produced from afull-height bridge-type defect using a darkfield (DF) mode (HPEC) and abrightfield (BF) mode on a 2830 Brightfield Patterned Wafer DefectInspection System produced by KLA-Tencor Corporation, Milpitas, Calif.,for an inspection target having a 5 nm coating of inspection enhancementmaterial over a 30 nm DR NIL structure with a 40 nm depth photoresist(e.g. as shown in FIG. 1) as a function of the inspection wavelength. Asshown, aluminum provides signal enhancement in both DF and BF thatincreases associated defect signals above the uncoated case.

Using the simulated wavelength data, wafer inspection tool parametersmay be analyzed to determine how a wafer inspection tool's signal can beimproved. FIG. 3 shows signals in BF and DF for the 2830 BrightfieldPatterned Wafer Defect Inspection System produced by KLA-TencorCorporation, Milpitas, Calif., using the inspection recipe for thevarious topical inspection enhancement layer 103A materials optimized toresult in the maximum signal responses.

A particular topical inspection enhancement layer 103A material may haveproperties that allow resonant surface plasmons to occur. The potentialfor such occurrences is a function of the permittivity of the topicalinspection enhancement layer 103A. The occurrence of surface plasmonmodes for some materials and their use as a component of the topicalinspection enhancement layer 103A may be desirable. FIGS. 4A and 4B showscattering cross sections as a function of wavelength where values >1indicate a potential signal improvement due to a topical inspectionenhancement layer 103A. FIG. 4B shows a large potential signalenhancement using a typical noble metal as a topical inspectionenhancement layer 103A material having a negative permittivity relativeto surrounding material permittivity, a necessary condition to supportsurface plasmon resonance modes. In contrast, FIG. 4A shows moderatepotential signal enhancement from a typical dielectric material thatcannot readily support surface plasmon resonance modes.

Referring to FIG. 5, an inspection target 100 is shown. The inspectiontarget 100 may include at least one inspection enhancement underlayer103B configured as a transparent underlayer disposed under an inspectionlayer 101. Such a configuration may result in a thin-film interferenceeffect having an interference maximum at the location of defectstructures 102. The thin-film interference can be caused by lightreflecting off a substrate 104, and may also reflect off of interlayerboundaries between transparent or semi-transparent materials in thestack (e.g. the boundary between inspection layer 101 and inspectionenhancement underlayer 103B) interfering with incident and otherreflected light thereby producing standing waves of maximum and minimumelectric field intensities. By varying the optical properties (e.g. therefractive index n; the extinction coefficient k) and thickness of theinspection enhancement underlayer 103B, the location of the maximum andminimum electric field within the depth in the inspection layer 101 orother transparent material can be changed and optimized to conform tothe inspection wavelength as described below. The inspection target 100may also include at least one inspection enhancement underlayer 103Bconfigured as a opaque underlayer disposed under an inspection layer101. In addition to enhancing defect signal, this underlayer may havethe added advantage of reducing wafer inspection noise from underlyingprocess variation and previous layer defects.

The inspection layer 101 may be generally applied in a thin layer 40-100nm thick over a Si blank wafer substrate 104 and then developed for thepurpose of testing a stepper tool's focus and exposure or to qualify themask by inspecting a print-check wafer for mask defects. It may be thecase that an optimal wavelength for inspecting such samples may beshorter than current wafer inspection tools utilize. Developing a waferinspection tool that operates at shorter wavelengths may be costly dueto limited and very expensive light sources available, expensive opticsand poor optical coating performance, increased risk of photocontamination, wafer damage from high-energy photons to name a fewdisadvantages. By selecting the material and thickness of the inspectionenhancement underlayer 103B, the signal producing properties of thesample may be adjusted such that the maximum inspection wavelengths aremoved to within the operating wavelength range for an inspection tool.The interference effect may also be used to maximize the signal bymoving the standing wave maximum to the location of the defect. Forexample, a resulting signal may be a function of the electric field atthe defect location and, as such, may change with wavelength of theincident light as the wavelength determines where the maximum andminimum of the standing wave interference will occur. Changing thethickness or material of the underlying layer may alter the interferenceproperties of the stack to maximize the electric field at the defect.This may be done for a particular wavelength or, if a wavelength isknown, at a particular location within the structure where the defect islocated. It should be noted that such techniques may be used with theother methods to increase signal as well (e.g., the pattern transfertechnique as will be discussed below).

Particularly, the optimum inspection wavelength may be moved to awavelength range where the potential damage from the inspection photonsaltering the chemistry of the inspection layer 101 is minimized. Toillustrate the effect, a variable thickness SiN inspection enhancementunderlayer 103B was simulated beneath an inspection layer 101 and thedefect signal in a brightfield low-sigma mode (VIB) from a full-heightbridge defect was calculated as a function of the thickness of the SiNinspection enhancement underlayer 103B and inspection wavelength. FIG. 6shows various signal responses for various inspection enhancementunderlayer 103B thicknesses across various wavelengths. As shown in FIG.6, the uncoated inspection layer 101 may have a maximum wavelengthsensitivity at about 230 nm. Such sensitivity may be below inspectionthresholds for broadband wafer inspection tools that operate between 260and 450 nm. As shown, by selecting a depth of 25 nm for the SiNinspection enhancement underlayer 103B, the maximum may be moved toabout 300 nm, inside the broadband spectrum and much above the uncoatedinspection layer 101 signal. Other thicknesses may be employed to movethe signal responses toward other portions of the spectrum that might beadvantageous for minimizing noise (which may also be a function of thewavelength) or minimizing wafer damage by photochemical processes.

If the inspector has a particular light budget maximum at a particularwavelength, the maximum of the defect signal can be tuned to thatwavelength by varying the depth and/or material properties (e.g. n, k)of the inspection enhancement underlayer 103B. FIG. 7 illustrates thiseffect by showing the signal as a function of the depth of a SiNinspection enhancement underlayer 103B for 313 nm and 365 nm. As shown,to obtain a maximum signal response at an inspection wavelength of 365nm, a SiN inspection enhancement underlayer 103B depth of either about40 nm or about 140 nm may be selected depending upon which thicknessmight be better suited to the requirements of other wafer processingsteps. It will be recognized that transparent materials other than SiNmay be used to create a thin-film interference effect (e.g., SiO2).

Still further, signal response may be improved by transferring apatterned inspection layer 101 of an inspection target 100A onto aninspection enhancement underlayer 103B of a second inspection target100B. By selecting an inspection enhancement underlayer 103B that hasstronger scattering properties, the corresponding defects of theinspection layer 101 may be easier to capture. Such processes aresimilar to after-etch inspection techniques but are, instead, applied toa short loop wafer (e.g. wafers used to test a particular step in thefabrication process) with one or more under-layer materials that hasoptimum inspection properties rather than a processed full-loop wafer(e.g. a wafer in a production line). In this way an image pattern and animage of the defect (protrusion, bite, bridge, etc), may be transferredinto a material stack with a selected depth, materials and composition.Defect sensitivity may be greater in after-clean inspection (ACI) layers(e.g. as shown in FIG. 8C) than after-develop inspection (ADI) layers(as shown in FIG. 8A). The stack may be designed to exploit materialcontrast versus wavelength, scattering power of materials (i.e. higherindex of refraction), and interference effects as described above. Ifthe wavelengths in a selected inspection band are able to penetrate astack, the overall volume of the defect scattering center may beincreased by increasing defect height. Further, line-space structures(common in photo short loop studies) that have behaved like opticalwaveguides when the material, dimension, wavelength and incident angleare correctly tuned have been observed. This waveguide effect may beexploited to amplify the E-field in the direct vicinity of the defect ofinterest.

Referring to FIGS. 8A-8C, a pattern transfer technique for an inspectiontarget 100 is shown. An original pattern of an inspection layer 101 on asilicon substrate 104 of an inspection target 100A (as shown in FIG. 8A)may be patterned on a stack (e.g. a thicker SiN inspection enhancementunderlayer 103B with an underlying SiO₂ adhesion layer 105 as shown inFIGS. 8B and 8C) of a second inspection target 100B. The inspectionlayer 101 pattern of the inspection target 100A may be etched into theSiN inspection enhancement underlayer 103B of the second inspectiontarget 100B, and then cleaned prior to inspection (e.g. ACI) to removeetched portions of the SiN topical inspection enhancement layer 103A toleave a patterned inspection enhancement underlayer 103B as shown inFIG. 8C. The patterned inspection enhancement underlayer 103B may thenbe subjected to inspection.

The patterned inspection enhancement underlayer 103B material may beselected to include a higher scattering material than the inspectionlayer 101 of inspection target 100A and its thickness and the thicknessof an underlying layer (e.g. adhesion layer 105) can be used to move thebest signal wavelengths into the range of a wafer inspection tool asdescribed above. Additionally, the depth of the adhesion layer 105 maybe similarly adjusted to provide an additional degree of optimization.

Referring to FIG. 9, simulated performance by a 2830 BrightfieldPatterned Wafer Defect Inspection System produced by KLA-TencorCorporation, Milpitas, Calif., on various pattern transfer materials asa function of their thickness is shown. The simulated signals obtainedfrom analysis of an ADI configuration (as shown in FIG. 8A) were used asa normalization factor with the simulated plot signals obtained from anACI configuration (as shown in FIG. 8C) relative to the ADI for both BFand DF. As shown in FIG. 9, a relatively thick SiN may have the bestperformance especially in DF where signal increases of >30× arepossible. Material choices for the underlayer can include SiN, SiO2,Poly Si, Si, Al, TaN, TiN, and the like.

Referring to FIG. 10, the wavelength response for the ACI configurationwith various thickness of SiN inspection enhancement underlayer 103Bcompared with the wavelength response for the ADI configuration withoutthe inspection enhancement underlayer 103B show that the wavelength forenhanced sensitivity may be optimized to correspond with favorableregions by configuring the thickness of the SiN inspection enhancementunderlayer 103B. A similar effect can occur by varying the thickness ofone or more underlying materials (e.g. adhesion layer 105) to move thebest signal to a desired wavelength.

Still further, signal response may be improved by selecting inspectionlayer 101 materials (e.g. photoresist layers) and/or adding dyes (e.g.to increase absorption) to the inspection layer 101 to enhance opticalproperties of the inspection layer 101 at inspection wavelengths. Byselecting an inspection layer 101 with a refractive index of 1.9, thescattering enhancement can increase by 3.7 compared to a inspectionlayer 101 with a refractive index of 1.58 over the spectral range of the2830 Brightfield Patterned Wafer Defect Inspection System produced byKLA-Tencor Corporation, Milpitas, Calif.

FIG. 11A shows the increase in simulated defect signal as a function ofrefractive index n at the inspection wavelengths using a darkfield (DF)mode (HPEC) and a brightfield low-sigma mode (VIB) brightfield mode on a2830 Brightfield Patterned Wafer Defect Inspection System produced byKLA-Tencor Corporation, Milpitas, Calif., and for both reflective andabsorptive underlayers. FIG. 11B shows the increase in simulated defectsignal in a low-sigma mode (VIB) brightfield mode as a function ofextinction coefficient k at the inspection wavelength for a reflectiveunderlayer. By increasing k from 0 to 1.0, the simulated defect signalincreases by 1.9×. The extinction coefficient k can be increased atinspection wavelengths by adding dyes whose absorption peaks arecentered on the inspection mean wavelength. The refractive index can beincreased at inspection wavelengths by selection of inspection layer 101materials or by adding absorbers with absorption peaks at shorterwavelengths than the inspection wavelengths. The index of refractionnaturally increases near the absorption peak for wavelengths longer thanthe absorption peak (normal dispersion).

The foregoing detailed description has set forth various embodiments ofthe devices and/or processes via the use of block diagrams, flowchartsand/or examples. Insofar as such block diagrams, flowcharts and/orexamples contain one or more functions and/or operations, it will beunderstood by those within the art that each function and/or operationwithin such block diagrams, flowcharts or examples can be implemented,individually and/or collectively, by a wide range of hardware, software,firmware or virtually any combination thereof. In one embodiment,several portions of the subject matter described herein may beimplemented via Application Specific Integrated Circuits (ASICs), FieldProgrammable Gate Arrays (FPGAs), digital signal processors (DSPs), orother integrated formats. However, those skilled in the art willrecognize that some aspects of the embodiments disclosed herein, inwhole or in part, can be equivalently implemented in integratedcircuits, as one or more computer programs running on one or morecomputers (e.g., as one or more programs running on one or more computersystems), as one or more programs running on one or more processors(e.g., as one or more programs running on one or more microprocessors),as firmware, or as virtually any combination thereof, and that designingthe circuitry and/or writing the code for the software and or firmwaremay be well within the skill of one of skill in the art in light of thisdisclosure. In addition, those skilled in the art will appreciate thatthe mechanisms of the subject matter described herein may be capable ofbeing distributed as a program product in a variety of forms, and thatan illustrative embodiment of the subject matter described hereinapplies regardless of the particular type of signal bearing medium usedto actually carry out the distribution. Examples of a signal bearingmedium include, but may be not limited to, the following: a recordabletype medium such as a floppy disk, a hard disk drive, a Compact Disc(CD), a Digital Video Disk (DVD), a digital tape, a computer memory,etc.; and a transmission type medium such as a digital and/or an analogcommunication medium (e.g., a fiber optic cable, a waveguide, a wiredcommunications link, a wireless communication link (e.g., transmitter,receiver, transmission logic, reception logic, etc.), etc.).

In a general sense, those skilled in the art will recognize that thevarious aspects described herein which can be implemented, individuallyand/or collectively, by a wide range of hardware, software, firmware, orany combination thereof can be viewed as being composed of various typesof “electrical circuitry.” Consequently, as used herein “electricalcircuitry” includes, but is not limited to, electrical circuitry havingat least one discrete electrical circuit, electrical circuitry having atleast one integrated circuit, electrical circuitry having at least oneapplication specific integrated circuit, electrical circuitry forming ageneral purpose computing device configured by a computer program (e.g.,a general purpose computer configured by a computer program which atleast partially carries out processes and/or devices described herein,or a microprocessor configured by a computer program which at leastpartially carries out processes and/or devices described herein),electrical circuitry forming a memory device (e.g., forms of randomaccess memory), and/or electrical circuitry forming a communicationsdevice (e.g., a modem, communications switch, or optical-electricalequipment). Those having skill in the art will recognize that thesubject matter described herein may be implemented in an analog ordigital fashion or some combination thereof.

The herein described subject matter sometimes illustrates differentcomponents contained within, or connected with, different othercomponents. It is to be understood that such depicted architectures maybe merely exemplary, and that in fact many other architectures may beimplemented which achieve the same functionality. In a conceptual sense,any arrangement of components to achieve the same functionality iseffectively “associated” such that the desired functionality isachieved. Hence, any two components herein combined to achieve aparticular functionality can be seen as “associated with” each othersuch that the desired functionality is achieved, irrespective ofarchitectures or intermedial components. Likewise, any two components soassociated can also be viewed as being “operably connected”, or“operably coupled”, to each other to achieve the desired functionality,and any two components capable of being so associated can also be viewedas being “operably couplable”, to each other to achieve the desiredfunctionality. Specific examples of operably couplable include but maybe not limited to physically mateable and/or physically interactingcomponents, and/or wirelessly interactable, and/or wirelesslyinteracting components, and/or logically interacting, and/or logicallyinteractable components.

In some instances, one or more components may be referred to herein as“configured to,” “configurable to,” “operable/operative to,”“adapted/adaptable,” “able to,” “conformable/conformed to,” etc. Thoseskilled in the art will recognize that “configured to” can generallyencompass active-state components and/or inactive-state componentsand/or standby-state components, unless context requires otherwise.While particular aspects of the present subject matter described hereinhave been shown and described, it will be apparent to those skilled inthe art that, based upon the teachings herein, changes and modificationsmay be made without departing from the subject matter described hereinand its broader aspects and, therefore, the appended claims may be toencompass within their scope all such changes and modifications as maybe within the true spirit and scope of the subject matter describedherein. It will be understood by those within the art that, in general,terms used herein, and especially in the appended claims (e.g., bodiesof the appended claims) may be generally intended as “open” terms (e.g.,the term “including” should be interpreted as “including but not limitedto,” the term “having” should be interpreted as “having at least,” theterm “includes” should be interpreted as “includes but is not limitedto,” etc.). It will be further understood by those within the art thatif a specific number of an introduced claim recitation is intended, suchan intent will be explicitly recited in the claim, and in the absence ofsuch recitation no such intent is present. For example, as an aid tounderstanding, the following appended claims may contain usage of theintroductory phrases “at least one” and “one or more” to introduce claimrecitations. However, the use of such phrases should not be construed toimply that the introduction of a claim recitation by the indefinitearticles “a” or “an” limits any particular claim containing suchintroduced claim recitation to claims containing only one suchrecitation, even when the same claim includes the introductory phrases“one or more” or “at least one” and indefinite articles such as “a” or“an” (e.g., “a” and/or “an” should typically be interpreted to mean “atleast one” or “one or more”); the same holds true for the use ofdefinite articles used to introduce claim recitations. In addition, evenif a specific number of an introduced claim recitation is explicitlyrecited, those skilled in the art will recognize that such recitationshould typically be interpreted to mean at least the recited number(e.g., the bare recitation of “two recitations,” without othermodifiers, typically means at least two recitations, or two or morerecitations). Furthermore, in those instances where a conventionanalogous to “at least one of A, B, and C, etc.” is used, in generalsuch a construction is intended in the sense one having skill in the artmay understand the convention (e.g., “a system having at least one of A,B, and C” may include but not be limited to systems that have A alone, Balone, C alone, A and B together, A and C together, B and C together,and/or A, B, and C together, etc.). In those instances where aconvention analogous to “at least one of A, B, or C, etc.” is used, ingeneral such a construction is intended in the sense one having skill inthe art may understand the convention (e.g., “a system having at leastone of A, B, or C” may include but not be limited to systems that have Aalone, B alone, C alone, A and B together, A and C together, B and Ctogether, and/or A, B, and C together, etc.). It will be furtherunderstood by those within the art that typically a disjunctive wordand/or phrase presenting two or more alternative terms, whether in thedescription, claims, or drawings, should be understood to contemplatethe possibilities of including one of the terms, either of the terms, orboth terms. For example, the phrase “A or B” will be typicallyunderstood to include the possibilities of “A” or “B” or “A and B.”

With respect to the appended claims, those skilled in the art willappreciate that recited operations therein may generally be performed inany order. In addition, although various operational flows may bepresented in a sequence(s), it should be understood that the variousoperations may be performed in other orders than those that may beillustrated, or may be performed concurrently. Examples of suchalternate orderings may include overlapping, interleaved, interrupted,reordered, incremental, preparatory, supplemental, simultaneous,reverse, or other variant orderings, unless context dictates otherwise.With respect to context, even terms like “responsive to,” “related to orother past-tense adjectives may be generally not intended to excludesuch variants, unless context dictates otherwise.

Although specific dependencies have been identified in the claims, it isto be noted that all possible combinations of the features of the claimsmay be envisaged in the present application, and therefore the claimsmay be to be interpreted to include all possible multiple dependencies.It is believed that the present disclosure and many of its attendantadvantages will be understood by the foregoing description, and it willbe apparent that various changes may be made in the form, constructionand arrangement of the components without departing from the disclosedsubject matter or without sacrificing all of its material advantages.The form described is merely explanatory, and it is the intention of thefollowing claims to encompass and include such changes.

1. A method for wafer defect inspection comprising: providing aninspection target; applying at least one defect inspection enhancementto the inspection target.
 2. The method of claim 1, further comprising:illuminating the inspection target including the at least one inspectionenhancement to generate one or more inspection signals associated withone or more features of the inspection target; detecting the inspectionsignals; generating one or more inspection parameters from theinspection signals.
 3. The method of claim 1, wherein the applying atleast one defect inspection enhancement to the inspection targetcomprises: applying a topical inspection enhancement layer to at least aportion of the inspection target.
 4. The method of claim 3, wherein theapplying a topical inspection enhancement layer to at least a portion ofthe inspection target comprises: applying a topical inspectionenhancement layer including at least one of: titanium nitride, aluminum,silver, gold, tantalum nitride and chromium.
 5. The method of claim 3,wherein the applying a topical inspection enhancement layer to at leasta portion of the inspection target comprises: applying a topicalinspection enhancement layer including a component exhibiting resonantsurface plasmons upon illumination.
 6. The method of claim 1, whereinthe applying at least one defect inspection enhancement to theinspection target comprises: disposing one or more inspectionenhancement underlayers under at least a portion of one or more layersof the inspection target.
 7. The method of claim 6, wherein thedisposing one or more inspection enhancement underlayers under at leasta portion of one or more layers of the inspection target comprises:disposing one or more inspection enhancement underlayers under at leasta portion of one or more layers of the inspection target where theinspection enhancement underlayer creates a thin-film interferenceeffect.
 8. The method of claim 7, wherein the disposing one or moreinspection enhancement underlayers under at least a portion of one ormore layers of the inspection target where the inspection enhancementunderlayer creates a thin-film interference effect comprises: disposingone or more inspection enhancement underlayers under at least a portionof one or more layers of the inspection target where the inspectionenhancement underlayer creates a thin-film interference effect having amaximum intensity at a location of a defect structure.
 9. The method ofclaim 7, further comprising: configuring at least one of a refractiveindex of the inspection enhancement underlayer, a coefficient ofextinction of the inspection enhancement underlayer and a thickness ofthe inspection enhancement underlayer to modify resulting inspectionsignals of the inspection target to correspond to an operating range ofan inspection device.
 10. The method of claim 6, wherein the disposingone or more inspection enhancement underlayers under at least a portionof one or more layers of the inspection target comprises: disposing oneor more inspection enhancement underlayers including at least one ofsilicon nitride and silicon dioxide to at least a portion of theinspection target under at least a portion of an inspection layer of theinspection target.
 11. The method of claim 6, wherein the disposing oneor more inspection enhancement underlayers under at least a portion ofone or more layers of the inspection target comprises: disposing two ormore inspection enhancement underlayers including a first inspectionenhancement underlayer that absorbs at exposure wavelength and transmitsat inspection wavelength and a second inspection enhancement layer thatreflects at inspection wavelength to at least a portion of theinspection target beneath an inspection layer of the inspection target.12. The method of claim 1, wherein the applying at least one defectinspection enhancement to the inspection target comprises: transferringa patterned inspection layer associated with the inspection target to asecond inspection target.
 13. The method of claim 12, whereintransferring a patterned inspection layer associated with the inspectiontarget to a second inspection target comprises: applying at least oneinspection enhancement layer to at least a portion of the secondinspection target; applying a patterned photoresist layer correspondingto the patterned inspection layer of the inspection target to the secondinspection target over the at least one topical coating; exposing thepatterned photoresist layer of the second inspection target; and etchingthe patterned photoresist layer of the second inspection targetphotoresist into the at least one inspection enhancement layer of thesecond inspection target.
 14. The method of claim 13, wherein theapplying at least one inspection enhancement layer to at least a portionof the second inspection target comprises: applying at least oneinspection enhancement layer including at least one of silicon nitrideand poly silicon.
 15. The method of claim 13, further comprising:configuring one or more thicknesses of the inspection enhancement layerto optimize the inspection signals.
 16. The method of claim 1, whereinthe applying at least one defect inspection enhancement to theinspection target comprises: incorporating one or more materials intoone or more inspection layers to modify at least one of a refractiveindex and an extinction coefficient of the one or more inspection layersat one or more inspection wavelengths.
 17. The method of claim 16,wherein the incorporating one or more materials into one or moreinspection layers to modify at least one of a refractive index and anextinction coefficient of the one or more inspection layers at one ormore inspection wavelengths comprises: incorporating one or morematerials into one or more photoresist inspection layers to modify atleast one of a refractive index and an extinction coefficient of the oneor more photoresist layers at the one or more inspection wavelengths.18. The method of claim 17, wherein the incorporating one or morematerials into one or more photoresist inspection layers to modify atleast one of a refractive index and an extinction coefficient of the oneor more photoresist layers at the one or more inspection wavelengthscomprises: adding one or more dyes to the one or more photoresistinspection layers to modify at least one of a refractive index and anextinction coefficient of the one or more photoresist inspection layersat the one or more inspection wavelengths.
 19. The method of claim 1,wherein the applying at least one defect inspection enhancement to theinspection target comprises at least two of: applying a topicalinspection enhancement layer to at least a portion of the inspectiontarget; disposing one or more inspection enhancement underlayers underat least a portion of one or more layers of the inspection target;transferring a patterned inspection layer associated with the inspectiontarget to a second inspection target; and incorporating one or morematerials into one or more inspection layers to modify at least one of arefractive index and an extinction coefficient of the one or moreinspection layers at one or more inspection wavelengths.
 20. Aninspection target comprising: at least one inspection layer; and atleast one inspection enhancement layer.
 21. The inspection target ofclaim 21, where in the at least one inspection layer comprises: at leastone photoresist layer.
 22. The inspection target of claim 21, whereinthe at least one inspection enhancement layer comprises: at least onetopical inspection enhancement layer disposed over the inspection layer.23. The inspection target of claim 22, wherein the at least oneinspection enhancement layer comprises: at least one patternedinspection enhancement underlayer disposed beneath the inspection layer.24. The inspection target of claim 23, wherein the at least onepatterned inspection enhancement layer comprises: at least one patternedinspection enhancement underlayer disposed beneath the inspection layer,the patterned inspection enhancement underlayer corresponding to apattern layer of a second inspection target.
 25. The inspection targetof claim 21, where in the at least one inspection layer comprises: oneor more materials modifying at least one of a refractive index and anextinction coefficient at an inspection wavelength relative to at leastone of a refractive index and an extinction coefficient of an inspectionlayer lacking the one or more materials.